The scarcity of female science professors is probably due to a combination of all the reasons above and others. It is essential, therefore, that we educate all academics about the equality of choice.

Photograph 51, the play starring Nicole Kidman as Rosalind Franklin, which opens in the West End this week, has put the role of women in science firmly on to the agenda. Dr Franklin was a top scientist instrumental in the discovery of DNA - but because she did not receive proper recognition for her work during her lifetime - she has become a feminist icon too.

In 2015, 57 years after Dr Franklin's tragically young death from cancer, the prospects for female scientists remain stubbornly poorer than their male peers, despite the decades of striving for equal opportunities.

In the School of Life Sciences at the University of Sussex where I work, we welcome undergraduates in a gender ratio of about 50:50%. In some subjects there are more women than men. But, as the career pathway progresses, there is a severe drop off in gender ratio, so that by Professorial level, there are just seven of us women, compared to 31 men.

In Britain's University sector as a whole the picture is even worse - with 91 per cent of professors male.

This tells us that we are losing talented women from academic science but the big question is why?

The answers are complex. Some suggest it because women make difficult choices when it comes to their work life balance. Having children places a difficult burden of choice on parents and particularly on mothers, but I am convinced this is not the full story.

Some would suggest that women "lack confidence." Anecdotally, women tend to apply for jobs only when they possess over 90 % of the desired criteria in the job specification, whilst men will apply when they are far less qualified. This is of course a generalisation, but talking to junior women in my department, I often hear the words: "I can't apply because I am not experienced in all of the criteria."

This also applies when women fail to seek promotion and it is clear that Universities need to find those who deserve promotion, rather than wait for people to apply. Some argue that role models should be used here to provide females with evidence that they can succeed in science.

Dr Franklin is of course a role model - and one who inspired me. Her contributions to science were, however, only really known by other scientists until the publication of "the double helix" book which was written by James Watson. The book unfairly depicted Dr Franklin as "awkward, difficult to work with and non-collaborative."

In fact she was highly collaborative and hugely mourned by colleagues and her PhD students. She had a strong drive for science but was an interesting and well -rounded person who loved the outdoors.

This brings me to the third reason for the drop off in women in science - unconscious bias. In a paper published in the Proceedings of the National Academy of Science some years ago, male and female academics were provided with CVs from a woman and a man. The CVs were identical except for the names. Yet the perceptions of the CVs was very different, judging the man as "more capable and hireable" and allocating him a higher salary. The bias was shown by both male and female academics. This ought to make us realise that we must be constantly vigilant and ready to challenge our unconscious bias.

The scarcity of female science professors is probably due to a combination of all the reasons above and others. It is essential, therefore, that we educate all academics about the equality of choice. We should all have the potential to choose our career pathway, without outside influence and we should be provided with the tools to help us. We can use role models from the past and we can highlight and celebrate the work currently being carried out by female scientist.

The School of Life Sciences here at the University of Sussex recently organised a symposium named after Rosalind Franklin. It was attended by our very own biomedical sciences student, Hannah Franklin and her father Nigel Franklin who are the great niece and the nephew of Rosalind.

We invited world renowned female scientists to speak about everything from Chemistry to Zoology, from bird flight navigation to RNA splicing. The reaction to the symposium was universally excellent.

The audience was visibly inspired by the range of subjects and by the career paths of the scientists - many of whom have struggled against the odds - just like Rosalind Franklin.